Switch tube device for wave guides



Dec. 20, 1949 w. M. HALL E1-r AL SWITCH TUBE DEVICE FOR` WVEGUIDES Filed July 13, 1945 Patented Dec. 20, 1949 AWilliamflvl. HallyLexington, and J amesDrLe Van, Belmont, Mass., `as'slgnors -to `Raytheon Manul- `facturing Company Newton, `Mass.,

tion of Delaware a corpora Application 1111x111?, 1945, Serial 1Y0-604.858

(C1. fuseau) ,f5 Claims.

Our present invention relates to switching d evices, and more particularly, 'to a switch tube for controlling thepropagation oi electromagnetic energy through a hollow wave guide, `or-through a `coaxial transmission line, or through any other similar mechanism capable of conveying energy of the general character indicated.

fIt is the main object of our presentinvention to obtain such control byaltering the impedance Of a discontinuity in an energy-transmission system, such as one of those above referred to, whereby, at the will ofthe operator, said discontinuity may be made to appear tothe `energy being ,conveyed as an infinite impedance, or as a short circuit.

It is a further object of our present invention to provide a switch tube which enables, as nearly as is possible, the attainment iof the idealirnppedance conditions above described. Itis a still further object o f our present "invention to accomplish the foregoingjin a Vsimple and inexpensive manner.

These and other objects of my presentinvention, which will become nmore apparent as jthe detailed description thereof progresses, are attained, briefly, in the following manner:

For purposes of illustratiomit willibe assumed throughout this specificationthat the energytransmission system to which our :present invention is applied comprises alhollow, rectangular wave guide, and that the discontinuitypin `said wave guide consists of a transverse, rectangular opening in one of the lside Walls upon which terminate the e-lines of the propagated electromagnetic energy. There will obviouslyjbea high impedance between `the longer side edges of such an opening, and it is with the alteration ofthis impedance that our present invention is concerned.

`Secured `to the wave guide, over the abovementioned opening, is a waveguide section, whichis closed at one end, and open at ythe other so as to communicate withrthe interior` of wsaid wave guide.

Said waveguide section is `provided with a partition, which-is pervious tothe propagated energy, and which coaller-altes--withthel sidewalls and closed end of said wave-guide `sectionwto form a chamber containing an ionizable vatmosphere, for example, a mixture of helium and hydrogen at reduced pressures.

Disposed within said chamber is da pair electrodes, one, an anode, and the other, a cold cathode, said electrodes extending inwardly from opposite side Walls of the wave-guide section, and

being connected across a source of -ring voltage.

Said electrodes are solocated in said waveguide section Awith respect to the discontinuity to 4be controlled, and with respect to the closed end of said wave-guide SQQQIL that the 'Aelectrigal distance vlitetween said electrodes and said discontinuity always iemains equal tothe 1Vlength of Vanintegral number of halfwaves at th fire# quency o-f the propagated energy, `whether r not `thedevice is `"beingdined. f'l'hereforejwhen the device is Vfiring, the resultingshortlciciiit condition between said electrodes is reicted "at said discontinuity, and the vpropagated energy can continue `along the wave guide; "but, "when the deviceis not dri-ng, lthe open-circuit condi'- tion between said electrodesis reflected at"``aid diswntinuitr and .the -rapasated energy Cene@ pass thefinnite impedance presented thereto. A`

fl-nthe accompanying s pecicationwe shall Vlescribe, and inthe annexed drawing show,` an illustrative embodiment of lthe switch tubel fo'f our present invention.

`It is, however, to be clearly understood that we do aio-t Vwish `toloe limited tothe details-herein shown and described for purposes "of illustration only,` inasmuch as changes therein Vmay-be withoigit` the exercise ,of invention i and Awith-in M ;hve true spirit and scope of the claims hereto appended.

Fig. A1 is a perspective viewof alwave guide provided `with a switch tube made in Aaccordance with the principles of our present invention; and

fFig. 2 "is a-longitudinal sectional view taken substantially through the center of hsuch a switch tube.

"Refeflngllow m0?? ndtaj toihefleld illustrative embodiment of our present invention, and with particular reference -to the `clija-ifing illustrating the same, the numeral 5 generally designates an.-^energytransmission system, here shown inthe. iormoi a hollow, rectangular-wave guide comprising spaced `side wallsd and Leon nected byend walls` 3 and 19.

:The sid-e wall ,is l provided a transverse, rectangular @genios 1,0 ,unich tes tri above referred;todiscontnuity whose mp ce to theenergy travelling ,through ,the w. eI guide it, is ,desired toy cpntrl,,said opening rounded by nella ll t0 I4. formed .mth l and ,tiene fre. for apurpose later to be described."

The .swith time @four Present invention, .generally designated by jthereference character 45 is secured `to the wave guide 5 by being mounted upon and hermetically sealed, as at I6, to the upper edges of the walls II to I4, inclusive, said switch tube itself constituting a wave-guide section comprised of side walls I1 and I8 connected by end walls I3 and 26. Said wave-guide section is open at one end, where it meets the rising walls II to I4, inclusive, so as to communicate with the interior of the wave guide 5, and it is closed at its other end by a top wall 2 I The walls I1 to 2l), inclusive, of the tube I5 are` split, as at 22, to receive a partition 23 consisting of a conducting frame 24 provided with a central, rectangular aperture 25 in which is sealed a window 26 made of material which is pervious to electromagnetic energy, said window being of such size that it will pass a frequency band of appreciable width. The partition v23, together with the upper portions of the split Walls I1 to 20, inclusive, and the wall 2I, defines a hermetically sealed chamber 21 which is provided with an ionizable atmosphere, for example, a mixture of helium at a pressure of 22 mm., and hydrogen at a pressure of 2 mm., the presence of the hydrogen being desirable because of its relatively short deionization time.

In order to enable lling of the chamber 21 with the aforementioned atmosphere, the wall I8 is `provided with a tube 28 communicating with said chamber, the outer end of said tube being provided with a glass seal 29 upon completion of the filling operation.

A `Mounted in the opposite side walls I1 and I8 of the tube I5, so as to extend into the chamber 21, are an anode member 30 and a cathode member 3l, said electrodes being coaxially disposed in opposition to each other, and presenting a gap between their opposed ends.

The cathode member 3I, preferably, comprises a cathode cup 32 provided with a highly electronemitting coating 33 on its inner surface, said cup being secured to a suporting collar 34 which is internally threaded to receive a rod 35, in turn, imbedded in a glass bead 36. The latter is sealed to a conducting sleeve 31, threadedly engaged, as at 38, inthe wall I8 and extending outwardly therefrom, said sleeve being provided with a anged portion 39 over which fits another conducting sleeve 48, abutting the wall I8 at its inner end, and, like the sleeve 36, extending outwardly from said wall. The sleeves 31 and 40, together, constitute an R.F. choke to prevent radiation of electromagnetic energy from the rod 35.

The cathode support 34 is surrounded by an insulating collar 4i and this, in turn, is surrounded by a cathode shield 42.

The outer end of the rod 35 contacts a cap 43, as at 44, said cap seating over an insulating collar 45 surrounding the choke sleeve 46 at the base thereof.

The anode member 35, preferably, comprises a conducting rod 46 which is provided with an enlarged portion 46 slidably mounted in an externally threaded bushing 41, said bushing being hermetically sealed, as at 48, in a shouldered opening 49 formed in the wall I1. In order to maintain the chamber 21 air-tight, the opening 49 is covered by a centrally-apertured, exible diaphragm 50 secured, at its outer periphery, in the shouldered portion f said opening 49 and, at its central aperture, to a collar I formed on the anode rod 46.

.Engageable over the bushing 41 is an internally threaded cap 52 having a head 53 at its outer end which is receptive of the outer end 54 of the anode rod 46, said outer end 54 being provided with an annular channel 55 receptiveV of a pair of pins 56 transversely disposed in the head 53. After the pins 56 are in place, the head 53 is provided with a cap 53 to keep said pins from falling out. It will be noted that rotation of the cap 52 reciprocates the anode rod 46, whereby the gap between the opposed ends of the rod 46 and the cathode cup 32 may be adjusted for a purpose which will later become apparent. After this adjustment is made, the cap 52 is locked against rotation by means of a screw 52 threadedly engaged in said cap and bearing against the bottom wall, of an lannular recess 41 formed in the bushing 41.

Caps 44and 52 are connected, through conductors 51 and 58, and a switch 59, to a source of voltage 66, so that when the switch 59 is closed, a discharge takes place between the electrodes 30 and 3 I NoW, such a discharge has the eiect, together with the electrodes 38 and 3I, of introducing a low inductance between the walls I1 and I8 of the tube. The section of the tube between the electrodes and the end wall 2i can also be considered as presenting an inductance acrossthe tube at the location of the electrodes. The impedance, therefore, appearing at the location of the electrodes is that of these two inductances in parallel, and the resulting inductance must be taken into account in arriving at the location of the electrodes with respect to the discontinuity to be controlled. Taking this inductance into account the distance between Ythe electrodes and the discontinuity is made slightly less than the length of an integral number of half-waves at the operating frequency of the wave guide. Preferably this distance should lbe slightly less than a single half wave so that the low impedance condition bewteen the electrodes, which is reiiected at the discontinuity, will be a minimum. When such a low impedance condition obtains, the energy being propagated through the wave guide can continue past the discontinuity.V

On the other hand when the tube is not discharging, the electrodes 36 and 3| present a cer` tain capacitance between the walls I1 and I8. The electrodes are, therefore, designed and 'pro-r portioned so that the capacitance reactance is such that considering the distance between the electrodes and the end wall 2I of the tube, which has already been fixed, the impedance reflected at the discontinuity in the wave guide is a maxlmum, and the propagated energy is prevented from passing said discontinuity.

The location of the partition 23 is also quite critical. The window 26, carried by said partition, behaves as another resonant circuit in Yparallel with the wave guide at the location of said partition. In order, therefore, to minimize its effect the window is located electrically an odd number of quarter waves from the discontinuity inthe wave guide. At such a point the impedance with which the window is in parallel is extremely low when the tube is not discharging. Hence, any reactance introduced by the window-will have a minimum effect.

Finally, we have found it best to join the tube I5 to the wave guide at a point approximately an odd number of veighth waves from the discontinuity. At such a point, the effect of poorrcontact between the tube `and the wave guide is a minimum, both when the tube is discharging and whenits not. For this purpose, the rising walls Il-M, inclusive, are provided.

This` completes the description of the aforesaid illustrative embodiment of our present inventiene It will be noted from all of the foregoing that we have provided a simple switch tube for controlling the impedance of a discontinuity in a wave guide, whereby the energy being propagated through said wave guide maybe presented, at said discontinuity, with either a short-circuit condition, in which case, the energy can continue travelling through the wave guide,` or with an infinite impedance, in which case, the energy is prevented from travelling further down the wave guide.

Other objects and advantages of our present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

1. A switch tube for changing the impedance of a discontinuity in a hollow wave guide from infinity to a short circuit, comprising: a waveguide section closed at one end and open at the other; said open end being adapted to communicate with the interior of said hollow wave guide at said discontinuity; a partition disposed within said wave-guide section to form, in cooperation with the walls and closed end thereof, a chamber containing an ionizable atmosphere; and a pair of spaced electrodes disposed within said chamber and adapted t0 have a voltage applied thereto to cause an electrical discharge therebetween; the electrical distances between said partition and said discontinuity, and said electrodes and said discontinuity, being equal, respectively, to the length of an odd number of quarter-waves and slightly less than the length of an integral number of half-waves at the operating frequency of said wave guide; and the electrical distance between said electrodes and the closed end of said wave-guide section being equal to slightly less than the length of an odd number of quarter-waves at Said operating frequency.

2. A switch tube for changing the impedance of a discontinuity in a hollow wave guide from infinity to a short circuit, comprising: a Waveguide section closed at one end and 4open at the other; said open end being adapted to communicate with the interior of said hollow wave guide at said discontinuity; a partition, including a conducting frame having an iris closed by a glass window, disposed within said wave-guide section to form, in cooperation with the walls and closed end thereof, a chamber containing an ionizable atmosphere; and a pair of spaced electrodes disposed within said chamber and adapted to have a voltage applied thereto to cause an electrical discharge therebetween; the electrical distances between said partition and said discontinuity, and said electrodes and said discontinuity, being equal, respectively, to the length of an odd number of quarter-waves and slightly less than the length of an integral number of half-waves at the operating frequency of said wave guide; and the electrical distance between said electrodes and the closed end of said waveguide section being equal to slightly less than the length of an odd number of quarter-waves at said operating frequency.

3. A switch tube for changing the impedance of a discontinuity in a hollow wave guide from innity to a short circuit, comprising: a waveguide section closed at one end and open at the other; said open end being adapted to communicate: with the interior` of; said hollow Wave guide` at said discontinuity; apartition disposed within said wave-guide section to.. form, in cooperation with the, walls and closed end thereof, a chamber containing; an ionizable atmosphere; a pair of spaced electrodes disposed within said chamber and, adapted to have a voltage applied thereto to cause an electrical discharge therebetween; the electrical distances` between said partition and said discontinuity, and said electrodes and said. discontinuity, being equal, respectiyely, to the length of,` an odd number of quarter-waves and slightly less than the length of an integral number of half-waves at the operating frequency of said wave guide; and the electrical distance between said electrodes and the closed end oi said wave-guide section being equal to slightly less than the length of an odd number of quarter-waves at said operating frequency; and means to alter the spacing between `said electrodes.

4. A switch tube for changing the impedance of a discontinuity in a hollow wave guide from infinity to a short circuit, comprising: a waveguide section closed at one end and open at the other; said open end being adapted to communicate with the interior of said hollow wave guide at said discontinuity; a partition, including a conducting frame having an iris closed by a glass window, disposed within said wave-guide section to form, in cooperation with the walls and closed end thereof, a chamber containing an ionizable atmosphere; and a pair of spaced electrodes disposed within said chamber and adapted to have a voltage applied thereto to cause an electrical discharge therebetween; the electrical distances between said partition and said discontinuity, and said electrodes and said discontinuity, being equal, respectively, to the length of an odd number of quarter-waves and slightly less than the length of an integral number of half-waves at the operating frequency of said Wave guide; and the electrical distance between said electrodes and the closed end of said waveguide section being equal to slightly less than the length of an odd number of quarter-waves at said operating frequency; and means to alter the spacing between said electrodes.

5. A switch tube for changing the impedance of a discontinuity in a hollow wave guide from infinity to a short circuit, comprising: a waveguide section closed at one end and open at the other; said open end being adapted to communicate With the interior of said hollow wave guide at said discontinuity; a partition, including a conducting frame having an iris closed by a glass window, disposed within said wave-guide section to form, in cooperation with the walls and closed end thereof, a chamber containing a mixture of helium and hydrogen at reduced pressures; and a pair of spaced electrodes disposed within said chamber and adapted to have a Voltage applied thereto to cause an electrical discharge therebetween; the electrical distances between said partition and said discontinuity, and said electrodes and said discontinuity, being equal, respectively, to the length oi an odd number of quarter-waves and slightly less than the length of an integral number of half-waves at the operating frequency of said wave guide; and the electrical distance between said electrodes and the closed end of said wave-guide section being equal to slightly less than the length of an odd,

number of quarter-waves at said oeiatingv frequency; and means to alter the spacing between said electrodes.

WILLIAM M. HALL. JAMES D. LE VAN.

REFERENCES CITED The following references are of record in the l of this patent:

UNITED STATES PATENTS Number Name Date 2,106,770 Southworth Feb. 1, 1938 2,404,832 Espley June 11, 1946 Number OTHER REFERENCES R.. C. A. Publication, Practical Analysis of 0 Ultra High Frequency, by Meagher & Markley. Published August 1943 by R. C. A. Service Co.

Inc., Camden, New Jersey. 

